Phthalate esters are widely used as plasticisers for polyvinyl chloride. Examples of phthalate esters that are used include dioctyl phthalate, di-isononyl phthalate, di-isodecyl phthalate, di-isooctly phthalate, diisoheptyl phthalate and di-2-ethyl hexyl phthalate (DEHP). Typical commercial materials include the Jayflex plasticisers, Jayflex® DNP and Jayflex® DIDP available from ExxonMobil Chemical and the Palatinol® plasticisers marketed by BASF and Vestinol® from Oxeno.
The alcohols from which the plasticiser esters are made are generally obtained by either olefin oligomerisation followed by hydroformylation or by hydroformylation of olefins to form aldehydes followed by aldehyde dimerization, generally by an aldol reaction. The alkyl groups of the esters therefore vary in size and structure according to the process and raw materials used to produce the alcohols. Typical plasticiser esters contain alkyl groups of 5 to 13 carbon atoms, particularly 7 to 13 carbon atoms, and have varying degrees of branching. The size and structure of the alkyl group helps determine the volatility and gellation temperature of the plasticiser and is therefore chosen according to the application in which the plasticised polyvinyl chloride is to be used. For instance flooring, where stain resistance is required, high volatility, at least of the surface layer, is desired.
There is a constant need to improve the properties of plasticisers to provide polyvinyl chloride compositions having improved properties. There is also a need for alternative plasticisers. In addition there is a need to improve the properties of plasticisers. It has also been proposed that esters of cyclohexane carboxylic acids particularly esters of cyclohexane dicarboxylic acids may be used as plasticisers for polyvinyl chloride. For example United States defensive patent publication T 864003 discloses the use of cyclohexane 1-4 dicarboxylate esters as plasticisers. In particular T 864003 discloses bis(2-ethylhexyl)cyclohexane 1-4 dicarboxylate as a plasticiser and compares its performance with bis(2-ethylhexyl)phthalate and finds improved low temperature performance and comparable mechanical properties when using the cyclohexane based material. Such materials are also described in a Union Carbide Chemicals Company Technical Information bulletin Number F-7893B of November 1957 entitled “Flexol” Plasticiser CC-55.
More recently, Gebrauchsmuster DE 29824628 and PCT Publication WO 99/32427 disclose a range of plasticisers based on cyclohexane dicarboxylic acid prepared by the hydrogenation of the corresponding phthalates. According to DE 29824628 and WO 99/32427, the cyclohexanoates have lower density and viscosity and yield an improvement in the low temperature flexibility of the plastics when compared with the corresponding phthalates. Properties such as the Shore hardness and other mechanical properties of the resultant plastics are said to be identical to those obtained with the use of phthalates. According to WO 99/32427, the cyclohexanoates exhibit better workability in a dry blend and also have advantages through the markedly lower viscosity when compared with the corresponding phthalates.
Japanese Patent Application Publication Number P 2001 207002 describes cyclohexane dicarboxylic acid esters derived from mixtures containing from 80 to 97 wt % of C9 branched alcohols. Japanese Patent Publication Number P 2001-207002 compares, as plasticisers, these esters with dioctyl phthalate and finds improved cold resistance, viscosity and viscosity stability over time.